This invention relates generally to a hypodermic apparatus and more particularly to an improved injector assembly including two sub-assemblies adapted to be uniquely joined together and positively interlocked prior to use.
Two-part syringes for the injection of medicaments are well known wherein two sub-assemblies are threadedly connected to one another prior to use of the syringe. Prior art examples will be found U.S. Pat. No. 2,778,359 issued Jan. 22, 1957 to Friedman and U.S. Pat. No. 4,333,457 issued June 8, 1982 to Margulies. In both of these syringes, one of the sub-assemblies comprises a plunger rod slidably supporting a head member that is in turn, provided with either external or internal threads. This threaded member is adapted to threadedly engage mating threads formed adjacent the rear end of the syringe barrel or cartridge. To provide such a threaded connection on the cartridge sub-assembly it has been common to provide a metal or other construction at least at the rear end of the cartridge area since the cost and practicality of forming safe and reliable threads on the relatively thin stock of a conventional glass cartridge barrel rules out such latter approach.
By the present arrangement an improved cost effective syringe is provided wherein an interlocked injector assembly is offered for use with a conventional type of glass barrel. The firm interlock of the two sub-assemblies is achieved through the interaction of a first threaded connector element carried by the plunger rod and a second threaded connector element adapted to slidably surround the barrel. As the two threaded connector elements are tightened with respect to one another, a resilient or compressible sleeve contained between the second connector element and barrel is progressively axially compressed with a resultant progressive enlargement or at least radially inward displacement, thereby firmly securing the two interlock connector elements to the smooth external surface of the barrel.
Accordingly, one of the objects of the present invention is to provide an improved injector assembly including two threaded mating connector elements respectively carried by a plunger rod and adapted to surround a barrel, with a resilient member carried by one such element surrounding the external surface of the barrel and adapted to be axially compressed during interlocking of the connector elements.
A further object of the present invention is to provide an improved injector assembly including a plunger rod slidably supporting a first threaded connector element and a glass or the equivalent barrel adapted to be surrounded by a second threaded connector element and wherein with the two connector elements interlocked, a resilient sleeve captively engaged between the connector elements and the external surface of the barrel is longitudinally compressed and radially forced into a clamping action between the barrel and second connector element.
Still another object of the present invention is to provide an improved injector assembly including two threaded mating connector elements respectively carried by a plunger rod and adapted to surround a barrel, with a resillient member surrounding the external surface of the barrel and adapted to be axially compressed during interlocking of the connector elements.
A further object of the present invention is to provide an improved injector assembly including a plinger rod slidably supporting a first threaded connector element and a glass or the equivalent barrel adapted to be surrounded by a second threaded connector element and wherein with the two connector elements interlocked, a resilient sleeve captively engaged between the connector elements and the external surface of the barrel is longitudinally compressed and radially forced tolock the barrel to the second connector element.
Still another object of the present invention is to provide an improved injector assembly comprising plunger and barrel sub-assemblies each adapted to support a slidable threaded member and wherein interlocking of the two sub-assemblies is achieved without any direct threaded connection between the plunger sub-assembly and barrel.
With these and other objects in view which will more readily appear as the nature of the invention is better understood, the invention consists in the novel construction, combination and arrangement of parts hereinafter more fully described, illustrated and claimed with reference being more to the attached drawing.